Dresden 2003 – wissenschaftliches Programm

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M: Metallphysik

M 23: Mechanische Eigenschaften IV

M 23.2: Vortrag

Dienstag, 25. März 2003, 16:45–17:00, IFW B

In situ TEM study of dislocation processes at precipitate free zones in NIMONIC PE16 — •Dietmar Baither, Thorsten Krol, and Eckhard Nembach — Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Strasse 10, 48149 Münster

Precipitate free zones (PFZ) are formed in the γ^′-strengthened nickel-based superalloy NIMONIC PE16 along the grain boundaries (GB). They reduce the yield strength. The decrease in yield strength is governed by dislocation processes within the PFZ and near the boundary to the γ^′-strengthened interior of the grains. These processes were investigated by means of TEM in situ straining experiments.

Dislocations emitted at the GB pass through the PFZ easily, but are piled up near the boundary between the PFZ and the interior of the grains. Within the PFZ frequent cross slip and double cross slip of dislocations occurs. Cross slip is required to enable the compatible deformation of the neighbouring grains, but in addition, the pile up of dislocations enhances these cross slip processes. A consequence of frequent cross slip are many dislocation sources within the PFZ. Their intense dislocation emission during further straining increases the very localized pile ups further more. High local stresses arise and allow that dislocations penetrate into the interior of the grains at relatively low external stress.